Is External Wall Insulation (EWI) Worth The Investment 

External wall insulation (EWI) has become increasingly popular in recent years. EWI involves applying insulation material to the external walls of a building followed by a render finish or cladding system. This type of insulation offers several benefits, including improved thermal performance and energy efficiency, enhanced soundproofing capabilities and weather protection. The demand for EWI has increased due to the rising energy costs and the need for sustainable solutions that reduce carbon footprint.

In addition to this, homeowners and landlords alike are becoming more conscious of their environmental impact and are looking for ways to improve their home’s energy efficiency. This article aims to provide a comprehensive and expert guide to EWI by examining its benefits and whether installation of EWI is worth the initial investment.

What is External Wall Insulation (EWI)

External wall insulation is a method of insulating solid walls by fixing an insulating material to the external surface of a building’s external walls. The insulating layer is then covered with protective layers such as a render or cladding EWI system that not only protects but also enhances the aesthetic appeal of the property. 

The thickness of insulation used varies according to building requirements and can range from 50mm up to 200mm depending on factors such as location, climate conditions as well as local regulations.

This article asks the question, is external wall insulation worth it. It will provide an overview of the different benefits of EWI and will examine the cost effectiveness of EWI compared to traditional insulation methods whilst considering government grants and financial incentives available for EWI installation.

The Benefits of EWI

Increased Energy Efficiency and Lower Heating Bills

External Wall Insulation is an effective way to reduce energy consumption and save money on heating bills. By adding a layer of insulation to the external walls, heat is kept inside the building for longer, reducing the need for constant operation of heating systems.

This means that occupants can enjoy a more comfortable living environment without having to spend as much money on energy bills. Studies have shown that installing EWI can lead to energy savings of up to 40% (EWI thickness, EWI system, region and other factors dependent).

With the ever rising energy costs, investing in EWI can help protect bill payers from future price increases. Not only does this make financial sense for both homeowners and tenants, but it is also better for the environment as less energy is required to maintain a comfortable temperature in the home.

Improved Thermal Comfort and Reduced Condensation Risk

External Wall Insulation has been proven to improve thermal comfort within buildings by creating a more consistent and stable internal temperature. Because EWI systems are installed on the outside of the building, they eliminate cold spots and draughts commonly found in older buildings. This leads to a more pleasant living environment and healthier indoor air quality

In addition, EWI reduces condensation risk by preventing warm moist air from coming into contact with cold surfaces. This helps prevent dampness and mould growth which can lead to serious health problems such as respiratory issues.

Enhanced Sound Insulation and Noise Reduction

Another benefit of External Wall Insulation is its ability to provide enhanced sound insulation. The additional layer of insulation helps reduce noise transmission both inside and outside of the building. This is particularly important for those living in busy urban areas or next to noisy roads or train lines.

EWI has been shown to reduce noise levels by up to 10 decibels which can make a significant difference in terms of overall quality of life. In addition, sound insulation can also improve the value of the property as it makes it a more attractive and peaceful place to live.

Protection Against Weather Damage and Dampness

External Wall Insulation provides an effective barrier against weather damage and dampness. The insulation layer helps protect the external walls from extreme weather conditions such as heavy rain, wind, or snow. The finish (sometimes referred to as EWI cladding)  applied to the insulation can act as an effective barrier against moisture and weathering. The typical EWI finish which is composed of silicone render effectively protects the external surface of a building against weather conditions, but this can further be upgraded in regions that are affected even more by weathering. For example, seaside towns tend to adopt a pebble dash finish which is harder to wear against weathering caused by the sea, especially during the winter months

This added protection ensures that a building fitted with an EWI system is less susceptible to damage caused by water penetration. In addition, EWI systems are designed to be breathable which allows moisture to escape from within the building. This prevents moisture build-up within the walls which can lead to structural damage over time. By protecting against weathering, external Wall Insulation can help prolong the life of a building and reduce maintenance costs in the long run.

The Cost of EWI

Comparison between the cost of EWI and traditional insulation methods

External Wall Insulation (EWI) can be a more expensive method of insulating a building compared to traditional insulation methods, such as cavity wall insulation. The cost of EWI varies depending on factors such as the size of the property, type of materials used and complexity of installation.

However, the long-term benefits and cost savings from reduced energy bills make it an attractive investment for many property owners. 

Cavity wall insulation involves filling the gap between two walls with insulating material.

This method is cheaper than EWI but may not be suitable for all types of buildings. For example, older properties often have solid walls which cannot be insulated using cavity wall insulation.

Financial Considerations of Installing EWI 

When contemplating the installation of External Wall Insulation (EWI), it’s crucial to take into account the potential financial implications. The upfront cost of installation can be substantial, but it’s equally important to weigh this against the prospective savings on energy bills

Taking into account an average annual energy consumption of 20,000 kWh, and assuming that about 35% of this is lost through the walls, insulating the walls could lead to savings of approximately £277 per year on energy bills. Similarly, if we consider that around 25% of the heat loss is through the roof, insulating the roof could result in savings of approximately £198 per year. These estimates are based on the average price for gas in the UK in 2023, which stands at 4.65 pence per kWh.

The Return on Investment (ROI) and the payback period are also important factors to consider. For instance, if the cost of insulating the walls and the roof is £10,000, the ROI would be approximately 4.75%, and the payback period would be around 20 years. This implies that it would take roughly 20 years for the savings on the energy bill to match the initial investment of £10,000, not accounting for future energy rises which can further reduce the payback period.

However, the financial benefits of EWI extend beyond just energy savings. The installation of EWI can significantly increase the value of a property, making it more appealing to potential buyers. The enhanced energy efficiency and improved aesthetic appeal can add a substantial amount to the resale value of the property.

Furthermore, the comfort levels inside the property are greatly improved with EWI. The insulation helps maintain a consistent temperature inside the property, keeping it warm in winter and cool in summer. This can significantly enhance the living environment, providing a more comfortable and enjoyable space for occupants.

Lastly, it’s worth noting that EWI is a long-term investment. The insulation is designed to last for at least 25 years with minimal or no maintenance, making it a cost-effective solution in the long run. When you factor in these additional benefits, the case for investing in EWI becomes even stronger.

Exploring Financial Support for Solid Wall Insulation

Investing in solid wall insulation can be a significant expense, but there are avenues of financial support that can make this energy-saving home improvement more affordable.

Local Authority Funding

One of the first places to explore is your local authority. Many local governments offer grants or subsidies to homeowners looking to improve the energy efficiency of their homes. These programs are often part of broader initiatives to reduce carbon emissions and promote sustainable living. The specifics of these programs can vary greatly, so it’s essential to contact your local authority directly to understand what assistance might be available in your area. Other scheme such as the Local Authority Delivery (LAD) scheme are designed to help the most vulnerable.

National and Regional Energy Efficiency Programs

In addition to local authority funding there may be national or regional programs that provide financial support for energy efficiency improvements like solid wall insulation. These programs can take various forms including grants, low interest loans or tax credits. The eligibility criteria for these programs can vary, so it’s important to research and understand the specific requirements

ECO 4 Scheme and help with cost of EWI

All large utility companies with more than 150,000 customers are obliged to offer programs designed to assist customers in enhancing the energy efficiency of their homes. This initiative is the Energy Company Obligation (ECO) scheme, now in its fourth iteration, ECO4.

Under the ECO4 scheme, utility companies provide rebates or discounts on energy-efficient products and services. This includes support for solid wall insulation, making it a more affordable option for homeowners and landlords. By participating in the ECO4 scheme, property owners can significantly reduce the upfront costs of installing solid wall insulation, leading to long-term savings on energy bills and a more energy-efficient home

While the initial cost of installing solid wall insulation can be high various forms of financial support can help offset these costs. By exploring these options, homeowners can make this valuable home improvement more affordable, leading to long term savings on energy bills and a more comfortable, eco-friendly home

EWI Cost Vs Benefits Analysis

• The above table provides a rough estimate of costs and savings. For a more personalised and accurate analysis, it is recommended to consult with a professional EWI installer or architect.

Being creative with External Wall Insulation (EWI) Installation to save Cost

One effective strategy to manage the costs of installing External Wall Insulation (EWI) is to synchronise it with other home improvement projects. This approach can lead to significant savings in several ways.

Coordinating EWI Installation with Other Home Improvements

If you’re planning other renovations or repairs that require scaffolding or exterior work, it’s worth considering scheduling the EWI installation at the same time. For instance, if you’re replacing the roof, painting the windows or installing solar panels, the scaffolding would already be in place. This could save you the cost of setting up scaffolding solely for the EWI installation

Partial EWI Installation 

Another cost saving strategy is to consider partial installation. Instead of insulating the entire house at once, you could tackle it one section at a time. This approach allows you to spread the cost over a longer period, making it more manageable. If this approach is employed special consideration should be given to thermal bridging whilst the property is not fully insulated. Additional ventilation provisions should be considered for the period where not 100% of the property is insulated

EWI Installation alongside Repair and Redecoration

If a particular elevation of your house requires repair or redecoration, it could be an opportune time to install EWI. The process of installing EWI involves adding a layer of insulation material to the wall, then covering it with a special type of render or cladding. This not only improves the thermal efficiency of your home but also gives your exterior a fresh new look. Therefore, if a wall needs repair or redecoration, combining these tasks with EWI installation can be both cost-effective and efficient

While the upfront cost of EWI can be substantial, strategic planning and coordination with other home improvement projects can help optimise these costs. 

The EWI Installation Process

Installing External Wall Insulation (EWI) is a complex process that requires experienced and professional EWI installers. The installation process typically involves several steps, including preparation and surface cleaning, installation of insulation boards or panels, application of a basecoat and reinforcement mesh, and a final render or decorative finish.

Steps Involved in Installing EWI

The first step in installing EWI is to prepare the surface by removing any loose debris, dirt or paint from the walls. Then the walls are cleaned using pressure washers or other suitable methods to ensure that there is no residual dirt on the walls that would compromise the performance of the insulation system.

Next, insulation boards are fixed onto the wall using adhesives and mechanical fixings such as screws. These boards usually come in different thicknesses ranging from 20 mm to 200 mm and can be made of various materials such as expanded polystyrene (EPS), mineral wool, phenolic foam or polyurethane foam.

Once the insulation boards are installed correctly, a basecoat is applied over them followed by a reinforcement mesh. This mesh helps to distribute stresses evenly across the surface and provides additional strength to resist cracking on movement joints.

A decorative finish coat or render is applied over the reinforcement mesh. This topcoat can be made of various materials such as acrylic resin-based coatings or silicon renders which come in different colours and textures.

Different Types of Materials Used in EWI Installation

The type of material used for External Wall Insulation depends on various factors like thermal performance required; durability; budget; local climatic conditions; etc. Expanded Polystyrene (EPS) is one of the most common materials used due to its good thermal insulation properties at an affordable price point. Whilst EPS is a cheaper option it does not provide fire resistance and is not suitable for use in larger buildings or multiple properties. 

Mineral wool is an option that is fire-resistant and has excellent acoustic insulation properties. It is more expensive compared to EPS but has better moisture resistance and durability. Phenolic foam is a high-performance insulation material that offers good thermal conductivity without the need for greater EWI thickness. However, it’s relatively expensive compared to other options. 

Polyurethane foam provides the highest thermal insulation performance, but it’s also the most expensive of all options.

How to Choose a Reputable EWI Installer

Choosing a reputable installer for External Wall Insulation installation is crucial to ensure that the work complies with industry standards and regulations. Look out for installers who have certification from recognized professional bodies such as BBA (British Board of Agrément) or are PAS 2030 accredited for EWI installations. Another good practice is to check with system manufacturers for a list of recognised and recommended installers in your area. Manufacturer-recommended installers typically undergo training on specific EWI systems and show competence in installation of these EWI systems during actual projects.

Once satisfied EWI manufacturers typically issue ID cards showing competence, check these IDs before hiring EWI installers. 

Check if the installer has experience in similar projects and ask for references from previous clients. It’s also important to verify if they are fully insured and offer warranties on their workmanship.

Getting quotes from multiple installers will help you compare prices and quality of service offered by each installer. However, always remember not to compromise quality for lower price options as this can lead to future problems with your EWI system.

Choosing a professional EWI system installer can make or break your investment in External Wall Insulation. Do your due diligence by researching and verifying the qualifications, experience, references, insurance coverage, warranty offerings before selecting an EWI installer for your project

Choosing the right EWI installer checklist:

Drawback of installing EWI cheaply 

External Wall Insulation (EWI) can provide significant savings in cost of utility bills by reducing the amount of heat that escapes from a building. However, installing EWI cheaply might entail several potential drawbacks which makes the overall cost saving less significant or not worth it at all. . Some of these include:

Poor Quality of EWI Materials: Using lower cheap EWI materials often translates to compromise in quality and performance. Cheap EWI materials will more than likely not offer the same level of insulation or durability as a recognised and effective EWI system

Incorrect EWI Installation: If the EWI is not installed properly, it may not provide the intended insulation benefits. The detailing and finishing of the EWI system is of the utmost importance. Ignoring issues such as thermal bridging could be one of such factors and it is usually down to lack of training, experience, or attention to detail on the part of the EWI installers

Lack of Building Regulations Compliance: Cheap EWI installation might not comply with building regulations. This could affect the property insurance, fire safety of a property mortgages, refinancing and resale value of the property

Potential Damage to Building Structure: If not installed properly or if inappropriate materials are used, EWI can cause moisture to accumulate, which can lead to structural issues over time, including damp, mould and even structural failure

Shorter Lifespan: Cheap EWI materials might not last as long, meaning the EWI could need replacing sooner than if higher quality materials were used. The cost of removing existing EWI installations and replacing them with new is likely to cost significantly more than using a better quality EWI system in the first place 

Inadequate Energy Savings: If not properly installed, EWI may not provide the energy savings it’s designed to deliver. This could mean that the cost savings in terms of energy bills are less than expected

Aesthetic Issues: Cheaply done EWI may not look as good or offer as much flexibility in terms of finishes and styles. This could affect the building’s curb appeal and potentially its value

Final Thoughts 

After analysing the benefits, costs, installation process, and potential drawbacks of external wall insulation (EWI), it’s clear that EWI is a worthwhile investment for many homeowners and landlords. Not only does it improve energy efficiency and thermal comfort, but it also offers protection against weather damage and dampness. 

While the upfront cost of EWI may seem high compared to traditional insulation methods, the long term cost savings from reduced energy bills can make it a wise investment. Additionally, government grants and financial incentives are available to help offset the cost of installation. The improved sound insulation and noise reduction benefits can also add value to your home.

While there are many benefits of EWI, there are also some potential drawbacks to consider. 

For example, if not installed correctly, moisture build-up could occur  causing damage rather than protection against dampness. Additionally, the impact on the appearance and character of a building as well as neighbouring properties or conservation areas must be considered

External wall insulation (EWI) is worth considering for homeowners or landlords looking to improve their energy efficiency while enhancing thermal comfort in their homes. It’s important to weigh the costs carefully before making a decision but once you do decide on installing external wall insulation you will reap its benefits for years to come.. As with any home improvement project choosing skilled professionals can make all the difference and help mitigate potential risks. With the right EWI installer, the benefits of EWI can outweigh any potential drawbacks and offer a valuable investment into your home